Use case or problem
Currently, switching vaults (whether by using the Open Vault dialog or the quick vault switcher) will always open the new vault in a new window, leaving the old window behind.
This apparently is what many people want (depsite the teams’s initial beliefs¹, but it feels backwards for me: When I switch vaults, I switch context (notably between my work vault and my private vault). I never want the other vault open after switching – and keeping it open is actively harmful because it means my notes are one more tap away (tapping Obsidian in my Windows task bar now shows the picker with both windows instead of immediately opening Obsidian).
This means that what I’m currently doing very often is to use the vault switcher, Alt+Tab back, and Alt+F4 the other vault. But that gets old quickly 
Proposed solution
Please add a setting that makes the vault switcher behave like it does in the mobile apps: Switching vaults keeps the Obsidian window in place and simply loads in the newly selected vault.
Current workaround
You can play tricks with scripts³, but that’s obviously not ideal.
You can also merge your notes into a single vault, but this means you lose the ability to selectively share your synced vaults with different people.
Or you muscle-memory the Alt+Tab, Alt+F4 dance 
Related feature requests
- Help topic asking for how to do this
- identical wish on Reddit²
All links to Reddit, non-clickable because I can’t post links:
¹/r/ObsidianMD/comments/1dae63t/comment/l7jxify/
²/r/ObsidianMD/comments/1dax7nk/obsidian_16_is_it_possible_to_switch_vaults/
³/r/ObsidianMD/comments/1dax7nk/comment/n4v8ey8/